This proposal focuses on the central antibody and local B-lymphoid infiltrative responses to a human kidney allograft. After determining the maximum number of kidney antigens present in the normal organ, a new, highly sensitive two-dimensional electrophoresis method will be utilized to determine the total number and specificities of (allo)antibodies produced against the solubilized, radiolabelled and immunoprecipitated specific kidney antigens. Initial emphasis will be directed toward determining HLA vs. non-HLA antibodies, with subsequent electrophoretic definition of the most commonly occurring non-HLA specificities. The antibodies produced will be correlated with (a) donor-recipient HLA matching data, thus examining the relevence of HLA typing, and (b) with immunohistopathology studies of the rejected graft to evaluate the role of various antibodies in graft destruction. The local B-lymphoid infiltrative response will be evaluated by immunocytopathology utilizing peroxidase-anti-peroxidase staining for cell surface and intracytoplasmic immunoglobulin (Ig, IgG, IgM, IgA) positive infiltrating cells in fixed, counterstained tissue sections. Enumeration of the percentages of positive cells (non-plasma and plasma cells) will form the basis for examining (a) the evolution of the B-lymphoid infiltrates in protracted rejection, (b) the rate of evolution as related to HLA mismatches, (c) the role of B-cell infiltrates in irreversible graft tissue destruction, (d) correlation between B-cell populations in target tissue and those identified in harvested mononuclear cell isolates, and (e) correlations between B-cell populations in tissue and isolated populations subjected to hemolytic plaque assay for determinations of type and specificity of antibody secreted.